This invention relates to an electroconductive resin paste.
In the prior art, as the chip mount material onto a lead frame of IC, LSI, etc., there have been generally known the Au-Si eutectic alloy method, the solder method and the electroconductive resin paste method. However, the Au-Si eutectic alloy method is high in cost and there was involved the drawback that chip crack was generated when applied for a large scale chip. On the other hand, according to the solder method, for imparting soldering capability to IC chip, it is required to attach a film of Au on the back of the IC chip, whereby the cost is increased. Further, due to low melting point, there is the drawback that it is not applicable for a wire bonding device according to the thermal compression method (TC method) for which heating at 350.degree. C. is required. As compared with these methods, the electroconductive resin paste method is excellent in workability, reliability, heat-resistant adhesiveness, and it is also low in cost. Therefore, demand for this method is now increasing rapidly.
However, when a large scale chip such as memory is bonded and cured onto a copper lead frame with a large coefficient of thermal expansion (a) by use of this electroconductive resin paste, due to thermal stress created through the difference in between the chip and the lead frame, chip crack or chip warping is generated, whereby there has been involved the problem that yield in the assembling step or reliability of the device may be damaged.
The present invention is intended to remove the drawback of the electroconductive resin paste of the prior art as mentioned above and provide an electroconductive resin paste of high reliability without generation of chip crack even in a large scale chip.